IRON RIDGE, Wis. — Authorities are focusing their search for three missing teenage boys on an abandoned iron mine in southern Wisconsin.

Dodge County sheriff’s officials say the boys, ages 15 and 16, were last seen Sunday afternoon. Authorities say the boys’ bikes were found off a road near an entrance to an old abandoned mine near Iron Ridge.

At least a dozen police and fire departments are searching near the Neda Mine, including an area that’s densely wooded. The sheriff’s department identified the teens as Tate Rose and Zachary Heron, both 16, and 15-year-old Samuel Lein.

The mine is owned by the University of Wisconsin-Milwaukee which conducts bat research at the site. UWM says an estimated 100,000 bats live in the mine, which is among the Midwest’s largest winter shelters for hibernating bats.